Before a Cast session can begin, both the sender device and the receiver device (for example, a Chromecast) must be connected to the same wifi network. The display device (for example, a television) must be connected to the receiver device, either via the HDMI port or directly if it is an on-board device.

Hmm, I fail to see why there is a volume slider at all. You should be using the TV's volume control, in my opinion. The Chromecast should send "line level" audio to the TV. Having competing volume controls is inelegant.

So what do you do, leave your TV volume up high, so you can set an appropriate level in your other app/device? What happens when you switch inputs to another one with a higher volume level or line level? Ever blast yourself out?

Yes. Without cable and having horrible broadcast reception it seldom is a problem since we use the Chromecast for everything. But both Netflix and Hulu start at max so if we're not vigilant when it's loading we do blast ourselves out. Even if the CC would just remember which volume it was at last that'd be fine. We usually don't even know where the TV remote is. We have small kids so there's a million places it could be.